Forging press

ABSTRACT

A forging press comprises two press rams slidably movable against each other in rigid slide tracks by a drive including, for each ram, two eccentric shafts coupled for rotation in opposite senses, an eccentric carried by each shaft, a respective slide block surrounding each eccentric, an elliptic chuck containing the two slide blocks, a rotatable screw and thrust rod member extending centrally through the chuck between the slide blocks and having at one end screw threads in threaded engagement with screw threads on the associated press ram, and being corotationally connected at its other end to an adjusting gearing. The rod member is axially displaceable relative to the gearing.

United States Patent [191 Kralowetz [451 Sept. 10, 1974 1 FORGING PRESS[21] Appl. No.: 354,389

[30] Foreign Application Priority Data June 9, 1972 Austria 4975/72 [52]US. Cl. 72/407, 72/452 [51] Int. Cl B2lj 9/18 [58] Field of Search72/402, 403, 404, 407, 72/452 [56] References Cited UNITED STATESPATENTS 3,135,139 6/1964 Kralowetz 72/402 3,224,244 12/1965 Kralowetz .172/402 FOREIGN PATENTS OR APPLICATIONS 16,043 8/1889 Great Britain72/402 Primary Examiner-C. W. Lanham Assistant Examiner-Gene P. CrosbyAttorney, Agent, or Firm-Kurt Kelman [57] ABSTRACT A forging presscomprises two press rams slidably movable against each other in rigidslide tracks by a drive including, for each ram, two eccentric shaftscoupled for rotation in opposite senses, an eccentric carried by eachshaft, a respective slide block surrounding each eccentric, an ellipticchuck containing the two slide blocks, a rotatable screw and thrust rodmember extending centrally through the chuck between the slide blocksand having at one end screw threads in threaded engagement with screwthreads on the associated press ram, and being corotationally connectedat its other end to an adjusting gearing. The rod member is axiallydisplaceable relative to the gearmg.

2 Claims, 3 Drawing Figures PAIENIEU SEP 1 man FORGING PRESS Thisinvention relates to a high-speed forging press, which comprises twopress rams, which are slidable in rigid slide tracks and to act againsteach other and are adapted to be driven by eccentric shafts, slideblocks surrounding the eccentrics on said shafts, and elliptic chucks.

In the development of forging presses there is a trend toward largerforging forces and a higher number of strokes per minute so as to obtainlarger outputs per hour and forgings of higher quality. A large numberof strokes per minute and a small reduction per stroke are required fora uniform forging effect throughout the workpiece and oppose theformation of cracks and discontinuities A larger number of strokes perminute enables the use of a higher forging speed so that even relativelylarge workpieces can be forged down without intermediate heating becausea better utilization is enabled of the time within which the temperatureof the workpiece is lowered to the lowest temperature at which theworkpiece can be forged. The service life of the tools is of essentialsignificance for the economy and profitability of such forging press anddepends mainly on the time of contact between the tool and theworkpiece. This time of contact includes the time of the actualdeformation and the times in which the machine exhibits a resilientexpansion and contraction. Mainly in hydraulic presses the resilientexpansion and contraction take more time than the deformation. Anincrease of the time of contact is accompanied by an increase of theheat quantity which is transferred from the workpiece to the forgingtools. The tools may thus be heated until they are red hot and such ahigh temperature rise will obviously greatly increase the wear of thetools. This large heat transfer from the workpiece to the tool has alsoa highly adverse effect on the quality of the forging because it resultsin a premature formation of cracks on the surface and in a depressing ofthe surface.

For this reason, consideration must be given mainly to the overallresiliency behavior in the design of a high-speed forging press. Beforethe workpiece can be deformed, the spring excursions must be overcome,and this requires considerable work, which in an amount up to percentmust be considered as a loss because only part of the work of elasticstrain can be recovered. It will be understood that the spring capacityof the machine must be overcome and that this spring capacity is ofdecisive influence on the time of contact between the workpiece and thetool and consequently for the service life of the tool and the qualityof the forging. As soon as the tool has engaged the workpiece, thecontinued movement of the tool is opposed by the resistance of theworkpiece to deformation. This resistance exceeds the spring capacity ofthe machine so that the spring excursions which are inherent in thedesign of the machine must be overcome before the workpiece can bedeformed. Throughout this time, the tool is in close contact with theworkpiece, and the time of contact is virtually directly related to thespring excursion of the machine, which spring excursion is to beovercome.

For this reason, hydraulic forging presses are highly undesirablebecause in addition to the mechanical compliance of the variouscomponents of the machine, such as rams, press frame, and the likethereis a hydraulic compliance, which is a multiple of the strictlymechanical compliance and is due to the compressibility of the hydraulicfluid used in relatively large amounts, and to the elasticity of thepipelines and containers etc. which are required.

In the previously known, semihydraulic forging presses it has beenattempted to solve the problem which is due to the compliance in thatthe rams are hydraulically driven and mechanical means are used toadjust the stroke position. This enables a saving of large amounts ofhydraulic fluid so that the spring excursions can be considerablyreduced. These measures do not give satisfactory results, however, inforging presses operating at a particularly high speed and exerting highforging pressures.

As regards work of elastic strain and the spring excursions, thestrictly mechanical forging press is most desirable. The forging pressis mechanically driven, in most cases by eccentrics, and in its strokeposition can be adjusted by mechanical means, so that the springexcursions are within tolerable limits. A comparison of the springexcursions of a mechanical forging press, a semihydraulic forging pressand a fully hydraulic forging press shows that the use of a hydraulicfluid adds greatly to the spring capacity. For instance, in a presscapable of exerting a force of 1,000 metric tons, the spring excursionis about millimeters in a fully hydraulic plant, about 15 millimeters ina semihydraulic plant, and only 5 millimeters in a strictly mechanicalplant. It is apparent from these values that the times of contact varygreatly in the different types of machines.

A great disadvantage of mechanical forging presses, however, is the factthat they permit only of a relatively complicated and closely limitedadjustment of the stroke position because separate adjusting housingsare required for this purpose and large machine components are needed asthe forging forces increase. To enable the use of presently conventionalforging forces of up to 3,000 or 5,000 metric tons, the drivingeccentric shafts would have to be very large in diameter so that theirmanufacture would become too difficult and the size of their bearings inthe machine and consequently the overall size of the entire machinewould become intolerably large. Besides, in such large machines theexpenditure involved in the conventional means, such as adjustinghousings or the like, required to adjust the stroke position wouldhardly be justifiable. For this reason, the previously known, strictlymechanical forging presses can be used only to exert small forgingforces.

In view of the above it is an object of the invention to avoid theabove-described advantages and to provide a high-speed forging presswhich is of the kind described first hereinbefore and which has aminimum overall compliance, and which is as simple and rugged aspossible in structure and in which the stroke position can be adjustedwithin very wide limits and without accessories involving a largeexpenditure.

This object is essentially accomplished according to the invention inthat each press ram has associated with it at least two eccentricshafts, which are coupled to rotate in opposite senses, and that theassociated slide blocks are contained in a common elliptic chuck, whichis connected to the press rarn by a rotationally adjustable drivemechanism, which includes a screw, which serves also as a thrust rod andextends between the slide blocks centrally through the elliptic chuckand is rotatable in and axially fixed to said elliptic chuck and isguided at one end in female screw threads of the press ram and at theother end is corotationally connected and axially displaceable relativeto an adjusting gearing, preferably a worm gearing. Because thishighspeed forging press according to the invention is driven andoperated by strictly mechanical means, the spring excursion is minimizedand the at least two eccentric shafts provided for each press ramprevent an excessive increase of the dimensions of components ofmachines designed for exerting large forging forces. The load previouslyapplied to one eccentric shaft is shared by a plurality of such shaftsso that machines having components having approximately the samedimensions as before can be used to exert much larger forging forces.The slide blocks which are guided in a common elliptic chuck and whichduring the reciprocation of the press ram slide toward or apart fromeach other constrain the screw to move exactly in the axis of the pressram and ensure a steady and reliable operation of the press ram. Toenable an adjustment of of the stroke positions, the screw is guided byfemale screw threads of the press ram so that a rotation of the screwwill result in a change of the distance between the elliptic chuck andpress ram since the screw is axially fixed and rotatable relative to theelliptic chuck. The adjusting means, i.e., the screw, can be drivenbecause the same carries at its end remote from the press ram a drivewheel, which is part of an adjusting gearing and transmits its rotationto the screw. The drive wheel must be slidable along the axis of thescrew so that theadjusting gearing can be mounted in a fixed positionand yet the screw can perform its working movement without complicationsalthough the adjusting gearing is mounted in a fixed position. In thisconnection, the term working movement refers to the reciprocating motionwhich is imparted to the screw by the eccentrics, the slide blocks andthe elliptic chuck and which is transmitted by the screw to the pressram. There are virtually no limits to the range in which the press ramscan be adjusted because this range depends only on the axial extent ofthe female screw threads and of the screw-threaded portion of the screw.In spite of the advantages which can be achieved with this machine, thestructural expenditure remains within the conventional range and thestructure of the machine itself is sufficiently rugged to ensure anoperation involving no problems.

An embodiment of the invention is shown by way of example on theaccompanying drawing, in which FIG. 1 is a side elevation showing partlyin section a high-speed forging press according to the invention.

FIG. 2 is a sectional view taken on line lIII in FIG. 1, and

FIG. 3 is a sectional view taken on line Ill-III in FIG. 1.

The high-speed forging press generally designated 1 has two horizontallyguided press rams 2, which act against each other and are slidable inrigid slide tracks 4 in a forging box 3. Two eccentric shafts 5 areassociated with each press ram 2 and are coupled for joint rotation by aspur gearing 6. Each of the eccentric shafts 5 comprises an eccentric 7,which is surrounded by a slide block 8. The corresponding slide blocks 8move with mirror symmetry in a common elliptic chuck 9. The ellipticchuck 9 is connected to the press ram 2 by a mechanism which comprises ascrew 10, which is axially fixed in and rotatable relative to theelliptic chuck 9 and which transmits the movement of the elliptic chuckto the press ram. The screw 10 extends centrally through the ellipticchuck and between the slide blocks 8. It is guided at one end in femalescrew threads 11 of the press ram 2 and at the other end iscorotationally coupled to and axially displaceable relative to theadjusting gearing 12, which in most cases consists of a worm gearing.

The high-speed forging press 1 is driven by two synchronized motors 13.Each motor 13 rotates by means of clutches 14, 15 and intermediate geartrains 16 the eccentric shafts associated with a press ram 2 so that theworking motion is imparted to the press ram 2. To adjust the strokeposition of the press rams 2, the screw 10 serving as a thrust rod isrotated by the adjusting gearings 12, which are also synchronized. Thisresults in a change of the distance between the elliptic chuck 9 and thepress ram 2 and consequently in a change of the stroke position. Becausethe forging press according to the invention is driven by strictlymechanical means, it has only a small overall compliance so that only asmall spring excursion must be overcome in each working stroke of thepress rams. This affords the advantage that only a small loss isinvolved as this spring capacity is overcome and that the time ofcontact between the tool and workpiece is short. This is essential for ahigh quality of the forgings and for the profitability of the machine.

What is claimed is:

l. A forging press, which comprises a frame,

rigid slide track means carried by said frame,

two press rams, which are slidably movable against each other in saidslide track means, each of said press rams having female screw threads,

drive means for driving said press rams, said drive means including foreach of said'press rams at least two eccentric shafts, means couplingsaid eccentric shafts for rotation in opposite senses, two eccentrics,each carried by a respective one of said eccentric shafts, two slideblocks, each surrounding a respective one of said eccentrics, anelliptic chuck containing said two slide blocks, a rotatable screw andthrust rod member extending between said slide blocks centrally throughsaid elliptic chuck and being rotatable in and axially fixed to saidelliptic chuck and having at one end screw threads in threadedengagement with said female screw threads of the associated press ram,and

an adjusting gearing,

said screw and thrust rod member at its other end being corotationallyconnected and axially disadjusting gearing is a worm gearing.

1. A forging press, which comprises a frame, rigid slide track meanscarried by said frame, two press rams, which are slidably movableagainst each other in said slide track means, each of said press ramshaving female screw threads, drive means for driving said press rams,said drive means including for each of said press rams at least twoeccentric shafts, means coupling said eccentric shafts for rotation inopposite senses, two eccentrics, each carried by a respective one ofsaid eccentric shafts, two slide blocks, each surrounding a respectiveone of said eccentrics, an elliptic chuck containing said two slideblocks, a rotatable screw and thrust rod member extending between saidslide blocks centrally through said elliptic chuck and being rotatablein and axially fixed to said elliptic chuck and having at one end screwthreads in threaded engagement with said female screw threads of theassociated press ram, and an adjusting gearing, said screw and thrustrod member at its other end being corotationally connected and axiallydisplaceable relative to said adjusting gearing.
 2. A forging press asset forth in claim 1, in which said adjusting gearing is a worm gearing.